Paper: Combining Constituent Parsers

ACL ID N09-2064
Title Combining Constituent Parsers
Venue Human Language Technologies
Session Short Paper
Year 2009

Combining the 1-best output of multiple parsers via parse selection or parse hybridiza- tion improves f-score over the best indi- vidual parser (Henderson and Brill, 1999; Sagae and Lavie, 2006). We propose three ways to improve upon existing methods for parser combination. First, we propose a method of parse hybridization that recom- bines context-free productions instead of con- stituents, thereby preserving the structure of the output of the individual parsers to a greater extent. Second, we propose an efficient linear- time algorithm for computing expected f-score using Minimum Bayes Risk parse selection. Third, we extend these parser combination methods from multiple 1-best outputs to mul- tiple n-best outputs. We present results on WSJ section 23 and also on the English side of a Chi...